Re: [PATCH] kmalloc_percpu

[Rusty Russell <rusty@rustcorp.com.au>]

In message <1052187119.983.5.camel@rth.ninka.net> you write:
> On Mon, 2003-05-05 at 18:52, Andrew Morton wrote:
> > Rusty Russell <rusty@rustcorp.com.au> wrote:
> > > OK.  It has a size restriction: PERCPU_POOL_SIZE is the maximum total
> > > kmalloc_percpu + static DECLARE_PER_CPU you'll get, ever.  This is the
> > > main downside.  It's allocated at boot.
> > 
> > And is subject to fragmentation.
> > 
> > Is it not possible to go allocate another N * PERCPU_POOL_SIZE from
> > slab if it runs out?
> 
> No, then you go back to things requireing multiple levels of
> dereferencing.

Actually, you can; my previous patch did this.  But then all CPUS have
to be one continuous allocation: since modern big-SMP machines are
non-uniform, so you don't want this.

	http://www.kernel.org/pub/linux/kernel/people/rusty/patches/Misc/kmalloc_percpu-orig.patch.gz

> I think the fixed size pool is perfectly reasonable.

Yes.  It's a tradeoff.  I think it's worth it at the moment (although
I'll add a limited printk to __alloc_percpu if it fails).

Cheers,
Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.